NBC may be getting ready to roll out its summer shows, but it's already busy lining up celebrity tushes to fill those big, red leather judges' chairs on The Voice this fall.

Pharrell Williams has already signed on to replace Cee Lo Green, one of the original four coaches, who announced his departure in February; meanwhile,Christina Aguilera will likely be on a maternity break for the birth of her second child by the time Season 7 begins filming in June.

No Doubt frontwoman Gwen Stefani, who gave birth to her third son in late February, is rumored to be the lead candidate to take over Aguilera's chair, says The Hollywood Reporter, which, along with TheWrap.com, says the deal is in the works.

Williams brought Stefani onstage for a duet last weekend at Coachella last weekend, lending further credence to the rumors.

Stefani, 44, has previously been a guest mentor during the sixth season of American Idol, inspiring Sanjaya Malakar's infamous fauxhawk.